The present invention relates to an engine starter protecting device.
FIG. 1 is an explanatory diagram showing a conventional engine starter arrangement. In FIG. 1, reference numeral 1 designates a starter motor; 2, the rotary shaft of the starter motor 1; 3 and 4, stops fixedly mounted on the rotary shaft 2; 5, an engaging groove member; 6, an over-running clutch composed of an input rotary member 6a and an output rotary member 6b; 7, a pinion; and 8, an engire ring gear engaged with the pinion 7. Further in FIG. 1, reference numeral 10 designates an electromagnetic switch; 11, the plunger of the electromagnetic switch 10; 12, a spring adapted to push the plunger 11 outwardly (to the right in FIG. 1); and 13, a shift lever which turns about a rotating fulcrum 14. The shift lever 13 has an end portion (the lower end portion in FIG. 1) slidably engaged with the engaging groove member 5 so that the engaging groove member 5, the over-running clutch 6 and the pinion 7 are displaced between the stops 3 and 4 by the shift lever 13. When the electromagnetic switch 10 is not electrically energized, the end portion of the shift lever 13 is pushed towards the stop 3 by the elastic force of the spring 12.
The engaging groove member 5, the input rotary member 6a, the output rotary member 6b and the pinion 7 are fixedly secured to one another, and the inner wall of the input rotary member 6a is engaged with a helical spline gear (not shown) formed on the rotary shaft 2. The overdrive clutch 6 is so designed that the drive force of the starter motor 1 is transmitted from the input rotary member 6a to the output rotary member 6b; however, no power is transmitted in the opposite direction. That is, the clutch 6 is a one-way clutch.
FIG. 2 is a circuit diagram showing a conventional engine starter protecting device. In FIG. 2, reference numerals 1, 10 and 11 designate the starter motor, the electromagnetic switch and the plunger, respectively, which have been described with reference to FIG. 1; 17 and 18, a current coil (attracting coil) and a voltage coil (holding coil), respectively, which operate the plunger 11 when electrically energized; 19, a movable contact secured to the pluger 11; and 20 and 21, stationary contacts of the switch 10. When the switch 10 is not electrically energized, the switch 10 is maintained open by the spring 12 shown in FIG. 1. Further in FIG. 2, reference numeral 22 designates an auxiliary relay for electrically energizing the electromagnetic switch 10; 23, a keyswitch for starting the engine; 24, a battery; and 25, a protecting relay which is operated by the output of an alternator and includes a coil 25a and a normally-closed contact 25b. The protecting relay 25 is so designated that, when the output voltage of the alternator applied to the terminal L reaches a predetermined value, the normally closed contact 25b is opened by the magnetic force produced by the current in the coil 25a.
The operation of the conventional engine starter protecting device thus constructed will now be described.
When the keyswitch 23 is closed, the auxiliary relay 22 is energized since the normally closed contact 25b is closed when the engine is stopped. Accordingly, the contact of the auxiliary relay 22 is closed so that the current coil 17 and the voltage coil 18 of the electromagnetic switch 18 are electrically energized. As a result, the plunger 11 is operated and the shift lever 13 is turned counterclockwise (in FIG. 1) about the rotating fulcrum 14. Accordingly, the engaging groove member 5, the over-running clutch 6, and the pinion 7 are displaced rightwardly in FIG. 1 against the spring 12 until the pinion 7 engages with the ring gear 8. In this operation, the movable contact 19 of the electromagnetic switch 10 is engaged with the stationary contacts 20 and 21 so that the voltage of the battery 24 is applied to the starter motor 1 and the rotary shaft 2 is rotated. Therefore, the ring gear 8 is rotated through the over-running clutch 6 and the pinion 7. when the pinion 7 is not sufficiently engaged with the ring gear 8, the electromagnetic switch is not closed; however, as a limited current (auxiliary current) flows through the current coil 17 to the starter motor 1, the latter is rotated at a low speed. This causes the pinion 7 to normally engage with the ring gear 8.
When the output voltage of the alternator reaches the predetermined value after the start of the engine, the normally closed contact 25b of the protecting relay 25 is opened. As a result, the electromagnetic switch 10 is deenergized so that the plunger 11 is returned and the pinion 7 disengaged from the ring gear 8.
The conventional device described above suffers from the following drawback: If the engine stops during ordinary vehicle operation, the protecting relay 25 will not operate if the engine is rotating at a low speed due to an inertial force. Therefore, if the operator closes the keyswitch 23 quickly to make the starter motor 1 operate, the pinion 7 interferes with the ring gear 8 rotating at low speed, as a result of which the pinion 7 and the ring gear 8 will not satisfactorily engage with each other and may be damaged.
In view of the foregoing, an object of this invention is to provide an engine starter protecting device which, even when the engine is rotating at low speed, engagement of the starter's pinion with the engine's ring gear is prevented.